Chemical ordering and fragility minimum in Cu–As–Se glasses

Abstract Modulated Differential Scanning Calorimetric (MDSC) studies have been performed on Cu x As 40 Se 60− x glasses with x ranging between 0 and 30 at.%. The thermal parameters, namely the glass transition temperature ( T g ), the heat capacity ( C p ) and the jump in heat capacity at the glass transition (Δ C p ) are measured. The composition dependence of these thermal parameters has been found to exhibit interesting variations particularly at x = 20. Thermal crystallization studies show that the structural network is mainly characterized by the ternary Cu 3 AsSe 4 units with As 2 Se 3 and Cu 2 As 3 units depending on the concentration of Cu. These structural differences arising as a function of composition are reflected in the T g , C p and Δ C p . The observed transitions are also understood on the basis of Formal Valence Shell (FVS) model and the classification of strong and fragile liquids.